Content Distribution Networks (CDNs) place content in their points of presence (PoPs) either based on the popularity of the content or based on service level agreements (SLAs) with the content providers. Predicting the popularity of content or its access locality is done either retroactively (only after the content has already become popular at a global, national or regional scale), or proactively (when there is strong indication by the content providers that the content is expected to become popular).
According to various reports, some main drivers behind the growth of mobile data are social networks and streaming video. Social networks have become a dominant point of entry for the web. On social networks, a large fraction of the bandwidth is consumed by video and photographs shot by using a handheld and uploaded to the social network, which is then downloaded by people within the social circle of the user that uploaded the content.